1. Field of the Invention
The invention concerns improvements in packages for shipping pancakes of recording tapes such as magnetic recording tape. By a "pancake" is meant a great length of recording tape wound upon a flangeless core, the name being derived from the appearance of the wound tape.
2. Description of the Related Art
Manufacturers of magnetic recording tapes often ship packages of the tape in pancakes of sufficient length that each pancake will fill a large number of cartridges or cassettes, e.g., video cassettes of the VHS and Betamax formats. A typical package of n pancakes (usually 6 or 8) employs n+1 identical, interlocking divider trays or spacers of stiff expanded plastic such as polystyrene. Each of the spacers has an octagonal outer rim, a web extending inwardly from the rim and having flat areas against which the pancakes can rest, an annular recess between the web and the hub to allow the width of the core to be greater than that of the pancake, and a central hub which fits into the central opening of the core. Each web and each annular recess is covered by a soft cushion of expanded plastic, and the cushion sometimes is held in place by an adhesive. The package is constructed by fitting the central opening of the flangeless core of one pancake onto the hub of the first spacer, then alternately stacking spacers and pancakes, after which extruded plastic bands are wrapped around the completed stack, and the wrapped stack is placed in a corrugated fiberboard box. In the wrapped stack, the rims of the spacers are pressed tightly against each other, but it usually is possible to slip a piece of paper between a side of each pancake and the facing web of the spacer. Problems that have been encountered during shipment include axial movement of the core relative to the pancake (called "core drop"), offsetting of a portion of the pancake (called "upset"), rotation of the core relative to the pancake, and transfer of cushion adhesive to the tape. Furthermore, the fiberboard box is a source of debris which might contaminate the recording tape.
The company to which this application is assigned has been packaging magnetic recording tape pancakes as follows. Into a corrugated fiberboard box is placed a corrugated plastic sheet having two plastic facings and a central aperture into which is inserted a plastic aligning cylinder. Over this is placed a soft cushion of expanded plastic which has a central aperture that fits over the aligning cylinder. This is followed by a magnetic recording tape pancake, another cushion, a pancake, a cushion, and then another corrugated plastic sheet. The same sequence is repeated until the box has been filled with at least 6 pancakes. Upon shipment, core drop and core rotation have sometimes been encountered.
To unpack each of the packages described above, it is customary to grasp the inner diameter of the core and the outer convolution of tape between the thumb and fingers of one hand, and upon doing so, the outer convolution sometimes is damaged by slipping off the pancake. This damage can be greatly reduced by lifting the tape using both hands, but it can be difficult to get a good grasp of the outer convolution with both hands simultaneously.
U.S. Pat. No. 4,081,151 (Ender et al.) concerns the problem of transporting pancakes of magnetic recording tape on flangeless cores. The patent observes that because the winding surface of the core is wider than the tape, it has previously been "necessary to insert rings of foam or cardboard between the stacked reels of tape for transport" and to insert "cardboard sleeves into the axial bores of the winding cores" (col. 1, lines 18-38). The Ender patent provides stackable, interlocking flangeless cores by which a number of pancakes of magnetic recording tape can be stacked more compactly than in the prior art "without the aid of inserts, cardboard sleeves or the like to fix the cores in position" (col. 3, lines 26-30). That reference to "inserts" apparently indicates the elimination of the prior need to insert rings of foam or cardboard between the pancakes, but since the patent drawing illustrates a small space between adjacent pancakes, there appears to be nothing to prevent axial shifting of, and consequent damage to, the pancake.